1). Field of the Invention
This invention relates to a method of calibrating and using a semiconductor processing system.
2). Discussion of Related Art
Integrated circuits are commonly manufactured in and on semiconductor wafer substrates. A wafer substrate is then sawed into individual dice, each carrying a respective integrated circuit.
Various systems exist for processing wafer substrates. One such system is the Epi Centura® system by Applied Materials, Inc. of Santa Clara, Calif. The Epi Centura® system has a transfer chamber with a number of single-wafer processing chambers leading off the transfer chamber. Each wafer processing chamber is formed by upper and lower quartz windows. Infrared lamps outside the chamber radiate infrared radiation through the quartz windows into the chamber. A susceptor is located within the chamber, upon which a wafer substrate can be located. The wafer substrate can be heated from above, and the susceptor can be heated from below. The susceptor and the wafer substrate are both relatively thin, so that they are approximately the same temperature.
An upper pyrometer is located above the upper quartz window, and a lower pyrometer is located below the lower quartz window. Infrared radiation radiates from a layer formed on the wafer substrate through the upper quartz window to the upper pyrometer. Infrared radiation also radiates from a lower surface of the susceptor through the lower quartz window to the lower pyrometer. The pyrometers generate signals that vary in magnitude according to variations in magnitude of the infrared radiation. The infrared radiation, in turn, is roughly indicative of temperature of the layer and the lower surface of the substrate.
Errors in temperature value occur due to a number of factors. One reason why errors in temperature value occur is because of film deposited within the chamber after repeated use. Layers form on the lower surface of the susceptor and on inner surfaces of the quartz windows. The layer on the susceptor changes its emissivity, resulting in a change in an amount of infrared radiation therefrom, even if temperature remains constant. The layers on the quartz windows also attenuate infrared radiation, so that the magnitude of infrared radiation reaching the pyrometers is reduced, even at the same temperature. A further reason why errors in temperature value occur is because of changes in emissivity of a layer formed on some type of wafer substrate. The emissivity of the layer typically can change as it is formed. The change in the emissivity of the layer causes variations in the infrared radiation detected by the upper pyrometer, even at a constant temperature.